MCAD deficiency (MCADD; #OMIM 201450) is the most common inherited disorder of mitochondrial fatty acid oxidation. Already before the introduction of population newborn bloodspot screening (NBS), large phenotypic heterogeneity was observed between MCADD-patients, ranging between deceased patients and asymptomatic subjects. Most clinically ascertained patients were homozygous for the common c.985A\>G ACADM mutation. After NBS, newborns with novel ACADM-genotypes have been identified and subjects can be classified as either severe/classical or mild/variant MCADD-patients. Dietary management guidelines are based on expert opinion, limited experimental data summarized in one retrospective study on fasting tolerance in 35 MCADD patients. Interestingly, data are absent from fasting tolerance in MCADD patients between 0-6 months of age. These guidelines cause parental stress, especially for young patients. Moreover, the guidelines do not take into account the heterogeneity between patients, including the classification between severe versus mild MCADD-patients. The investigators question whether at least a subset of the MCADD-patients is overtreated with these guidelines. Therefore, the investigators propose this pilot-study on fasting tolerance in 10 subjects with severe MCADD and 10 subjects with mild MCADD at the ages of two and six months. Differences between subsets of MCADD-patients will be studied longitudinally by both traditional metabolic parameters and unbiassed metabolomics, lipidomics and proteomics approach. This project will substantiate current management guidelines and aims to identify new (prognostic) biomarkers.
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Change in blood glucose concentrations
Timeframe: Up to 8 samples will be taken during the maximally 8 hour fast (session 1), up to 12 samples will be taken during the maximally 12 hour fast (session 2).
Change in plasma free fatty acid (FFA) concentrations
Timeframe: Up to 8 samples will be taken during the maximally 8 hour fast (session 1), up to 12 samples will be taken during the maximally 12 hour fast (session 2).
Change in Heart rate
Timeframe: Up to 8 frequencies will be noted during the maximally 8 hour fast (session 1), up to 12 frequencies will be noted during the maximally 12 hour fast (session 2)
Change in Respiratory rate
Timeframe: Up to 8 frequencies will be noted during the maximally 8 hour fast (session 1), up to 12 frequencies will be noted during the maximally 12 hour fast (session 2).
(Change in) presence of lethargy
Timeframe: Up to 8 physical examinations will be performed during the maximally 8 hour fast (session 1), up to 12 physical examinations will be performed during the maximally 12 hour fast (session 2). Physical examinations will take 5 minutes.
(Change in) presence of trembling
Timeframe: Up to 8 physical examinations will be performed during the maximally 8 hour fast (session 1), up to 12 physical examinations will be performed during the maximally 12 hour fast (session 2). Physical examinations will take 5 minutes.